A new method for the long-term frequency stabilization of an opto-electronic oscillator (OEO) is proposed. All existing methods are based on the precise temperature stabilization of specific components of an OEO, for example, the optical fiber and the microwave band-pass filter. We propose a new method based on a feedback control loop that detects the oscillator frequency using a frequency discriminator and modifies the laser wavelength to keep the oscillator frequency constant using the fiber chromatic dispersion. With the proposed method we achieved a frequency-temperature coefficient of 0.2 ppm/K. Unlike previous methods, our method also compensates the effects of other unstabilized OEO components on the OEO's frequency. Other benefits are that there is no need for an accurate temperature stabilization of the optical fiber and mode hopping is prevented.

We present two stabilization methods for an opto-electronic oscillator. By using a frequency discriminator with a feedback control loop the long-term stabilization was improved, and a frequency drift of 0.05 ppm/K was achieved without any fiber thermal stabilization. In addition, the phase-noise degradation as a result of the discriminator control loop was investigated. To the best of our knowledge, this has not been done before for this type of method. Our study revealed that a properly designed control loop does not increase the phase noise. The second stabilization method was used to increase the side-mode suppression ratio. This was achieved with an additional control loop in the form of an oscillator-loop phase modulation. In this way, a 5-dB increase in the side-mode suppression ratio was recorded. The phase-noise degradation was less than 1 dB in the close-in region. The two methods were designed to operate simultaneously. This design provides both simplicity and cost effectiveness for the stabilized opto-electronic oscillator.

High-frequency signal oscillators are devices needed for a variety of scientific disciplines. One of their fundamental requirements is low phase noise in the micro- and millimeter wave ranges. The opto-electronic oscillator (OEO) is a good candidate for this, as it is capable of generating a signal with very low phase noise in the micro- and millimeter wave ranges. The OEO consists of an optical resonator with electrical feedback components. The optical components form a delay line, which has the advantage that the phase noise is independent of the oscillator’s frequency. Furthermore, by using a long delay line, the phase noise characteristics of the oscillator are improved. This makes it possible to widen the range of possible OEO applications. In this paper we have reviewed the state of the art for OEOs and micro- and millimeter wave signal generation as well as new developments for OEOs and the use of OEOs in a variety of applications. In addition, a possible implementation of a centralized OEO signal distribution as a local oscillator for a 5G radio access network (RAN) is demonstrated.